The present invention relates to pneumatic transportation arrangements in general, and more particularly to a pneumatic transporting arrangement for fiber flocks.
There is already known, for instance, from the German published patent application No. 15 10 413, a pneumatic transportation system for fiber flocks for supplying a plurality of carding devices in a transverse-feed fashion by means of a transporting medium through a duct of a constant cross section, a plurality of control members being arranged in the interior of such duct and being operative for controlling the flow of the transporting medium. In this system, an extraction roll is provided at the upper end of each chute which communicates with the interior of the duct and extends downwardly from the duct to the respective carding device. The extraction roll engages the flocks carried by the transporting medium and feeds them into the respective chute. The control members are constructed and arranged to serve as diverter plates that are pivotally mounted in the interior of the duct and divert the flocks from the respective extraction roll in the event that, in the absence of such diverting action, too many flocks would be captured by the extraction roll and fed thereby into the respective chute. This construction has the disadvantage that strong vortices form at the downstream ends and downwardly of the diverter plates, so that an undesirable accumulation of fiber flocks can form between the diverter plate and the surface of the duct which is situated below the diverter plate. Further drawbacks of this known construction are that the adjustability of the diverter plate is limited, that flock material can be fed into the duct only in one direction, and that full closure of the duct cannot be effected.
Furthermore, German published patent application No. 16 85 613 discloses a feed installation with a transport duct, wherein the cross-sectional areas of the duct passages situated between the chutes continuously increase from one chute to the next one. This serves to slow down the transporting air at the input end of the respective chute and to accelerate it again at the output end. In order to provide for control of the speed of the transporting air, there are provided insert plates arranged at the input and output openings of the feed chutes and extending normal to the direction of flow of the transporting air. The requirement for the insertion of such insert plates to adjust or control the flow speed is operationally impractical. Also, the disposition of the insert plates normal to the flow direction causes strong air turbulence and thus an increase in the energy required to produce the transport flow.
Swiss patent disclosure No. 370680 discloses an air duct in which pivotable diverter flaps are provided at the locations of the feed chutes and at the downstream side thereof with respect to the direction of the air flow. These diverter flaps serve to divert the fiber flocks into the respective feed chutes. The air acceleration caused by these diverter flaps occurs only at the rear side of the feed chutes and thus only after the fiber flocks have already substantially passed the chute opening. This, of course, is disadvantageous since it detracts from the precision of control of the amount of fiber flocks delivered into the respective chutes.